Ever ask what 20/20 vision really means? The term 20/20 eyesight represents a normal level of sharpness of eyesight or visual acuity determined from 20 feet away from the object. In other words an individual with such eyesight can clearly see an object at a distance of 20 feet that most individuals should be able to see from that distance.
For those who don't have 20/20 visual acuity, the number is assigned according to where they begin to see clearly in relation to what is normally expected. As an example, if your vision is 20/100 that means that at a distance of 20 feet you can only see what the baseline would see from 100 feet .
An individual with 20/200 visual acuity is considered blind, legally but can often achieve much improved eyesight through eyeglasses or contact lenses or by undergoing laser eye surgery if they are eligible.
An average eye screening is done by using an eye chart most commonly the classic Snellen eye chart developed by Dutch eye doctor, Herman Snellen in the 1860's. While today there are many versions, the chart generally has 11 lines of capital letters which get progressively smaller as one looks downward. The top of the chart usually shows one uppercase letter – ''E'' with letters being added gradually as you look down the chart. During the vision screening, the eye doctor will look for the smallest line of letters you can see clearly. Every line is given a rating, with the 20/20 row usually being assigned forth from the bottom. For young children, illiterate or disabled persons who are not able to read or vocalize letters, a variation of the chart is used called the ''Tumbling E''. At the same scale as the regular Snellen chart, this variation shows only the capital letter E in different rotations. The patient uses their hand to show which rotational direction the arms of the E are facing.. Both charts needs to be placed 20 feet away from where the patient is viewing it.
Despite common conception, 20/20 eyesight doesn't mean an individual has flawless eyesight but merely that they see well from a distance. There are many other necessary abilities needed to make perfect vision such as side or peripheral vision, perception of depth, focus for near vision, color vision and eye coordination to name a few.
It's important to remember that even though an eye exam using a Snellen chart can conclude if you need glasses to improve distance vision it doesn't provide the optometrist a comprehensive picture of your total eye health. Make sure you still schedule a yearly comprehensive eye exam which can identify potential conditions. Contact our office now to book an eye exam in Canton, OH.